For RF plasma supply devices and/or the RF generators that are arranged within a plasma supply device, nominal power levels are stipulated by the manufacturer, where the sum of the nominal power levels of the individual RF generators constitutes the nominal power of the plasma supply device.
RF generators and consequently RF plasma supply devices can be operated with a greater level of difficulty at a fraction of their nominal power. RF generators and RF plasma supply device can tend towards uncontrolled fluctuations and can be controlled at a precise power output with greater difficulty. In most cases, a lower power limit is also stipulated by manufacturers of RF generators, below which the RF generator cannot be operated in a reliable manner or with the required level of precision. For example, some manufacturers stipulate that the lower power limit is 10% of the nominal power, while some manufacturers stipulate an even lower value such as 1% of the nominal power. Moreover, the sum of the lower power limits of the RF generators constitutes approximately the lower power limit of the plasma supply device.
In order to operate the plasma supply device below the lower power limit, a first portion of the power from the RF generator is supplied to an additional resistor and the remainder of the power from the RF generator is supplied to the load to enable operation of the RF generator above the lower power limit. To this end, the resistor can be connected in series or in parallel with the load. For power levels below the lower power limit, this solution in most cases provides a usable result.